How to Build a Waterproof Shower Bench

The following is a unique step-by-step method for adding a
bench or seat to your shower that is simple, waterproof, extremely
durable because it's made out of concrete. After finding water
damage under several shower benches constructed of wood and lined
with waterproof membranes, I started making concrete shower benches
and have never had a single issue. I'll walk you through the
steps of the concrete shower bench and you'll see it's pretty slick.

The concrete shower bench should be added after hardiebacker and
waterproof membrane is painted on the walls. Determine the
size of your bench, in this case I created a bench 16" x 16" x 8",
and cut some scrap plywood up to form a box. Brace the bottom of the
form to keep it up tight against the wall when the concrete is
poured in. Add a few pieces of rebar or left over metal lathe
if you have some kicking around.

Another picture of the concrete bench formed up.

Mix up a few bags of Quikrete high strength concrete which cost
about $3.50/bag at Lowes. Slope the top of the bench away from
the wall about 1/4" so that water flows off the top of the bench
into the shower and not against the wall. Let the concrete dry
at least 24hrs.

Pull the forms off and there you have the concrete shower bench.

Tape the joints and cover the shower bench with a coat of thinset.

Paint the seat with Redgard or Aquadefense waterproofing membrane,
the same material used on the walls. With the concrete shower
seat you never have to worry about water damage. It's solid
concrete, and even if water migrates through the joints between the
seat and wall it will follow the wall down to the shower pan and
make its way to the drain the same way is would if the bench was not
there. The concrete shower bench provides a great surface to
apply tile to as well which is nice.